until she screens you, and actually is in the room alone with you, and she is comfortable with you, any suggestion, request or intimation could raise a red flag for her.

At some point in most sessions, you will be posed with the question of "what would you like?"  Feel free to tell her, but I would only ask for services she advertises, or is well known for providing (and I don't mean a listing on her profile, or a single review).  She can only say no, or maybe next time, but accept what is available.  I some cases, you will be surprized and get axactly what you want, it not go with the flow and enjoy the ride.

Once you had a successful encounter, it is much easier to suggest what you want so she can be prepared.

but anything more explicit should wait for a face to face.

Using reviews is the best way to know if the provider will by simpatico with your specific desires.

and try to make a determination from those, of what is available.  USUALLY if a provider is into specialties, it will be noted on her website.  Definitely leave any details OUT until you actually meet... in particular, any DOM who is really good, will actually take the time to interview you prior to your first session as to your likes, fetishes, etc.  After you get comfortable with each other, if you have picked well... the sky is the limit.